diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index fd718e2..64b839b 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -132,16 +132,6 @@
 	state = &sta->ampdu_mlme.tid_state_tx[tid];
 
 	if (local->hw.ampdu_queues) {
-		if (initiator) {
-			/*
-			 * Stop the AC queue to avoid issues where we send
-			 * unaggregated frames already before the delba.
-			 */
-			ieee80211_stop_queue_by_reason(&local->hw,
-				local->hw.queues + sta->tid_to_tx_q[tid],
-				IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
-		}
-
 		/*
 		 * Pretend the driver woke the queue, just in case
 		 * it disabled it before the session was stopped.
@@ -158,6 +148,10 @@
 	/* HW shall not deny going back to legacy */
 	if (WARN_ON(ret)) {
 		*state = HT_AGG_STATE_OPERATIONAL;
+		/*
+		 * We may have pending packets get stuck in this case...
+		 * Not bothering with a workaround for now.
+		 */
 	}
 
 	return ret;
@@ -226,13 +220,6 @@
 	       ra, tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
 
-	if (hw->ampdu_queues && ieee80211_ac_from_tid(tid) == 0) {
-#ifdef CONFIG_MAC80211_HT_DEBUG
-		printk(KERN_DEBUG "rejecting on voice AC\n");
-#endif
-		return -EINVAL;
-	}
-
 	rcu_read_lock();
 
 	sta = sta_info_get(local, ra);
@@ -267,6 +254,7 @@
 	}
 
 	spin_lock_bh(&sta->lock);
+	spin_lock(&local->ampdu_lock);
 
 	sdata = sta->sdata;
 
@@ -308,21 +296,19 @@
 			ret = -ENOSPC;
 			goto err_unlock_sta;
 		}
-
-		/*
-		 * If we successfully allocate the session, we can't have
-		 * anything going on on the queue this TID maps into, so
-		 * stop it for now. This is a "virtual" stop using the same
-		 * mechanism that drivers will use.
-		 *
-		 * XXX: queue up frames for this session in the sta_info
-		 *	struct instead to avoid hitting all other STAs.
-		 */
-		ieee80211_stop_queue_by_reason(
-			&local->hw, hw->queues + qn,
-			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
 	}
 
+	/*
+	 * While we're asking the driver about the aggregation,
+	 * stop the AC queue so that we don't have to worry
+	 * about frames that came in while we were doing that,
+	 * which would require us to put them to the AC pending
+	 * afterwards which just makes the code more complex.
+	 */
+	ieee80211_stop_queue_by_reason(
+		&local->hw, ieee80211_ac_from_tid(tid),
+		IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+
 	/* prepare A-MPDU MLME for Tx aggregation */
 	sta->ampdu_mlme.tid_tx[tid] =
 			kmalloc(sizeof(struct tid_ampdu_tx), GFP_ATOMIC);
@@ -336,6 +322,8 @@
 		goto err_return_queue;
 	}
 
+	skb_queue_head_init(&sta->ampdu_mlme.tid_tx[tid]->pending);
+
 	/* Tx timer */
 	sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.function =
 			sta_addba_resp_timer_expired;
@@ -362,6 +350,12 @@
 	}
 	sta->tid_to_tx_q[tid] = qn;
 
+	/* Driver vetoed or OKed, but we can take packets again now */
+	ieee80211_wake_queue_by_reason(
+		&local->hw, ieee80211_ac_from_tid(tid),
+		IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+
+	spin_unlock(&local->ampdu_lock);
 	spin_unlock_bh(&sta->lock);
 
 	/* send an addBA request */
@@ -388,15 +382,16 @@
 	sta->ampdu_mlme.tid_tx[tid] = NULL;
  err_return_queue:
 	if (qn >= 0) {
-		/* We failed, so start queue again right away. */
-		ieee80211_wake_queue_by_reason(hw, hw->queues + qn,
-			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
 		/* give queue back to pool */
 		spin_lock(&local->queue_stop_reason_lock);
 		local->ampdu_ac_queue[qn] = -1;
 		spin_unlock(&local->queue_stop_reason_lock);
 	}
+	ieee80211_wake_queue_by_reason(
+		&local->hw, ieee80211_ac_from_tid(tid),
+		IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
  err_unlock_sta:
+	spin_unlock(&local->ampdu_lock);
 	spin_unlock_bh(&sta->lock);
  unlock:
 	rcu_read_unlock();
@@ -404,6 +399,45 @@
 }
 EXPORT_SYMBOL(ieee80211_start_tx_ba_session);
 
+/*
+ * splice packets from the STA's pending to the local pending,
+ * requires a call to ieee80211_agg_splice_finish and holding
+ * local->ampdu_lock across both calls.
+ */
+static void ieee80211_agg_splice_packets(struct ieee80211_local *local,
+					 struct sta_info *sta, u16 tid)
+{
+	unsigned long flags;
+	u16 queue = ieee80211_ac_from_tid(tid);
+
+	ieee80211_stop_queue_by_reason(
+		&local->hw, queue,
+		IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+
+	if (!skb_queue_empty(&sta->ampdu_mlme.tid_tx[tid]->pending)) {
+		spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
+		/* mark queue as pending, it is stopped already */
+		__set_bit(IEEE80211_QUEUE_STOP_REASON_PENDING,
+			  &local->queue_stop_reasons[queue]);
+		/* copy over remaining packets */
+		skb_queue_splice_tail_init(
+			&sta->ampdu_mlme.tid_tx[tid]->pending,
+			&local->pending[queue]);
+		spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
+	}
+}
+
+static void ieee80211_agg_splice_finish(struct ieee80211_local *local,
+					struct sta_info *sta, u16 tid)
+{
+	u16 queue = ieee80211_ac_from_tid(tid);
+
+	ieee80211_wake_queue_by_reason(
+		&local->hw, queue,
+		IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+}
+
+/* caller must hold sta->lock */
 static void ieee80211_agg_tx_operational(struct ieee80211_local *local,
 					 struct sta_info *sta, u16 tid)
 {
@@ -411,15 +445,16 @@
 	printk(KERN_DEBUG "Aggregation is on for tid %d \n", tid);
 #endif
 
-	if (local->hw.ampdu_queues) {
-		/*
-		 * Wake up the A-MPDU queue, we stopped it earlier,
-		 * this will in turn wake the entire AC.
-		 */
-		ieee80211_wake_queue_by_reason(&local->hw,
-			local->hw.queues + sta->tid_to_tx_q[tid],
-			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
-	}
+	spin_lock(&local->ampdu_lock);
+	ieee80211_agg_splice_packets(local, sta, tid);
+	/*
+	 * NB: we rely on sta->lock being taken in the TX
+	 * processing here when adding to the pending queue,
+	 * otherwise we could only change the state of the
+	 * session to OPERATIONAL _here_.
+	 */
+	ieee80211_agg_splice_finish(local, sta, tid);
+	spin_unlock(&local->ampdu_lock);
 
 	local->ops->ampdu_action(&local->hw, IEEE80211_AMPDU_TX_OPERATIONAL,
 				 &sta->sta, tid, NULL);
@@ -602,22 +637,19 @@
 			WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);
 
 	spin_lock_bh(&sta->lock);
+	spin_lock(&local->ampdu_lock);
 
-	if (*state & HT_AGG_STATE_INITIATOR_MSK &&
-	    hw->ampdu_queues) {
-		/*
-		 * Wake up this queue, we stopped it earlier,
-		 * this will in turn wake the entire AC.
-		 */
-		ieee80211_wake_queue_by_reason(hw,
-			hw->queues + sta->tid_to_tx_q[tid],
-			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
-	}
+	ieee80211_agg_splice_packets(local, sta, tid);
 
 	*state = HT_AGG_STATE_IDLE;
+	/* from now on packets are no longer put onto sta->pending */
 	sta->ampdu_mlme.addba_req_num[tid] = 0;
 	kfree(sta->ampdu_mlme.tid_tx[tid]);
 	sta->ampdu_mlme.tid_tx[tid] = NULL;
+
+	ieee80211_agg_splice_finish(local, sta, tid);
+
+	spin_unlock(&local->ampdu_lock);
 	spin_unlock_bh(&sta->lock);
 
 	rcu_read_unlock();
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 6ce62e5..32345b4 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -639,6 +639,14 @@
 	struct sk_buff_head pending[IEEE80211_MAX_QUEUES];
 	struct tasklet_struct tx_pending_tasklet;
 
+	/*
+	 * This lock is used to prevent concurrent A-MPDU
+	 * session start/stop processing, this thus also
+	 * synchronises the ->ampdu_action() callback to
+	 * drivers and limits it to one at a time.
+	 */
+	spinlock_t ampdu_lock;
+
 	/* number of interfaces with corresponding IFF_ flags */
 	atomic_t iff_allmultis, iff_promiscs;
 
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index a7430e9..756284e 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -795,6 +795,8 @@
 	skb_queue_head_init(&local->skb_queue);
 	skb_queue_head_init(&local->skb_queue_unreliable);
 
+	spin_lock_init(&local->ampdu_lock);
+
 	return local_to_hw(local);
 }
 EXPORT_SYMBOL(ieee80211_alloc_hw);
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 4ba3c54..dd3593c 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -239,6 +239,11 @@
 		tid_tx = sta->ampdu_mlme.tid_tx[i];
 		if (tid_tx) {
 			del_timer_sync(&tid_tx->addba_resp_timer);
+			/*
+			 * STA removed while aggregation session being
+			 * started? Bit odd, but purge frames anyway.
+			 */
+			skb_queue_purge(&tid_tx->pending);
 			kfree(tid_tx);
 		}
 	}
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 5b223b2..18fd5d1 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -73,11 +73,13 @@
  * struct tid_ampdu_tx - TID aggregation information (Tx).
  *
  * @addba_resp_timer: timer for peer's response to addba request
+ * @pending: pending frames queue -- use sta's spinlock to protect
  * @ssn: Starting Sequence Number expected to be aggregated.
  * @dialog_token: dialog token for aggregation session
  */
 struct tid_ampdu_tx {
 	struct timer_list addba_resp_timer;
+	struct sk_buff_head pending;
 	u16 ssn;
 	u8 dialog_token;
 };
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index a0e00c6..906ab78 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -984,9 +984,9 @@
 	struct ieee80211_hdr *hdr;
 	struct ieee80211_sub_if_data *sdata;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
-
 	int hdrlen, tid;
 	u8 *qc, *state;
+	bool queued = false;
 
 	memset(tx, 0, sizeof(*tx));
 	tx->skb = skb;
@@ -1013,20 +1013,53 @@
 		 */
 	}
 
+	/*
+	 * If this flag is set to true anywhere, and we get here,
+	 * we are doing the needed processing, so remove the flag
+	 * now.
+	 */
+	info->flags &= ~IEEE80211_TX_INTFL_NEED_TXPROCESSING;
+
 	hdr = (struct ieee80211_hdr *) skb->data;
 
 	tx->sta = sta_info_get(local, hdr->addr1);
 
-	if (tx->sta && ieee80211_is_data_qos(hdr->frame_control)) {
+	if (tx->sta && ieee80211_is_data_qos(hdr->frame_control) &&
+	    (local->hw.flags & IEEE80211_HW_AMPDU_AGGREGATION)) {
 		unsigned long flags;
+		struct tid_ampdu_tx *tid_tx;
+
 		qc = ieee80211_get_qos_ctl(hdr);
 		tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
 
 		spin_lock_irqsave(&tx->sta->lock, flags);
+		/*
+		 * XXX: This spinlock could be fairly expensive, but see the
+		 *	comment in agg-tx.c:ieee80211_agg_tx_operational().
+		 *	One way to solve this would be to do something RCU-like
+		 *	for managing the tid_tx struct and using atomic bitops
+		 *	for the actual state -- by introducing an actual
+		 *	'operational' bit that would be possible. It would
+		 *	require changing ieee80211_agg_tx_operational() to
+		 *	set that bit, and changing the way tid_tx is managed
+		 *	everywhere, including races between that bit and
+		 *	tid_tx going away (tid_tx being added can be easily
+		 *	committed to memory before the 'operational' bit).
+		 */
+		tid_tx = tx->sta->ampdu_mlme.tid_tx[tid];
 		state = &tx->sta->ampdu_mlme.tid_state_tx[tid];
-		if (*state == HT_AGG_STATE_OPERATIONAL)
+		if (*state == HT_AGG_STATE_OPERATIONAL) {
 			info->flags |= IEEE80211_TX_CTL_AMPDU;
+		} else if (*state != HT_AGG_STATE_IDLE) {
+			/* in progress */
+			queued = true;
+			info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
+			__skb_queue_tail(&tid_tx->pending, skb);
+		}
 		spin_unlock_irqrestore(&tx->sta->lock, flags);
+
+		if (unlikely(queued))
+			return TX_QUEUED;
 	}
 
 	if (is_multicast_ether_addr(hdr->addr1)) {
@@ -1077,7 +1110,14 @@
 	}
 	if (unlikely(!dev))
 		return -ENODEV;
-	/* initialises tx with control */
+	/*
+	 * initialises tx with control
+	 *
+	 * return value is safe to ignore here because this function
+	 * can only be invoked for multicast frames
+	 *
+	 * XXX: clean up
+	 */
 	__ieee80211_tx_prepare(tx, skb, dev);
 	dev_put(dev);
 	return 0;
@@ -1188,7 +1228,8 @@
 	return 0;
 }
 
-static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
+static void ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
+			 bool txpending)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct sta_info *sta;
@@ -1202,11 +1243,11 @@
 
 	queue = skb_get_queue_mapping(skb);
 
-	WARN_ON(!skb_queue_empty(&local->pending[queue]));
+	WARN_ON(!txpending && !skb_queue_empty(&local->pending[queue]));
 
 	if (unlikely(skb->len < 10)) {
 		dev_kfree_skb(skb);
-		return 0;
+		return;
 	}
 
 	rcu_read_lock();
@@ -1214,10 +1255,13 @@
 	/* initialises tx */
 	res_prepare = __ieee80211_tx_prepare(&tx, skb, dev);
 
-	if (res_prepare == TX_DROP) {
+	if (unlikely(res_prepare == TX_DROP)) {
 		dev_kfree_skb(skb);
 		rcu_read_unlock();
-		return 0;
+		return;
+	} else if (unlikely(res_prepare == TX_QUEUED)) {
+		rcu_read_unlock();
+		return;
 	}
 
 	sta = tx.sta;
@@ -1251,7 +1295,12 @@
 			do {
 				next = skb->next;
 				skb->next = NULL;
-				skb_queue_tail(&local->pending[queue], skb);
+				if (unlikely(txpending))
+					skb_queue_head(&local->pending[queue],
+						       skb);
+				else
+					skb_queue_tail(&local->pending[queue],
+						       skb);
 			} while ((skb = next));
 
 			/*
@@ -1276,7 +1325,7 @@
 	}
  out:
 	rcu_read_unlock();
-	return 0;
+	return;
 
  drop:
 	rcu_read_unlock();
@@ -1287,7 +1336,6 @@
 		dev_kfree_skb(skb);
 		skb = next;
 	}
-	return 0;
 }
 
 /* device xmit handlers */
@@ -1346,7 +1394,6 @@
 		FOUND_SDATA,
 		UNKNOWN_ADDRESS,
 	} monitor_iface = NOT_MONITOR;
-	int ret;
 
 	if (skb->iif)
 		odev = dev_get_by_index(&init_net, skb->iif);
@@ -1360,7 +1407,7 @@
 		       "originating device\n", dev->name);
 #endif
 		dev_kfree_skb(skb);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	if ((local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) &&
@@ -1389,7 +1436,7 @@
 		else
 			if (mesh_nexthop_lookup(skb, osdata)) {
 				dev_put(odev);
-				return 0;
+				return NETDEV_TX_OK;
 			}
 		if (memcmp(odev->dev_addr, hdr->addr4, ETH_ALEN) != 0)
 			IEEE80211_IFSTA_MESH_CTR_INC(&osdata->u.mesh,
@@ -1451,7 +1498,7 @@
 	if (ieee80211_skb_resize(osdata->local, skb, headroom, may_encrypt)) {
 		dev_kfree_skb(skb);
 		dev_put(odev);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	if (osdata->vif.type == NL80211_IFTYPE_AP_VLAN)
@@ -1460,10 +1507,11 @@
 				      u.ap);
 	if (likely(monitor_iface != UNKNOWN_ADDRESS))
 		info->control.vif = &osdata->vif;
-	ret = ieee80211_tx(odev, skb);
+
+	ieee80211_tx(odev, skb, false);
 	dev_put(odev);
 
-	return ret;
+	return NETDEV_TX_OK;
 }
 
 int ieee80211_monitor_start_xmit(struct sk_buff *skb,
@@ -1827,6 +1875,54 @@
 		skb_queue_purge(&local->pending[i]);
 }
 
+static bool ieee80211_tx_pending_skb(struct ieee80211_local *local,
+				     struct sk_buff *skb)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_sub_if_data *sdata;
+	struct sta_info *sta;
+	struct ieee80211_hdr *hdr;
+	struct net_device *dev;
+	int ret;
+	bool result = true;
+
+	/* does interface still exist? */
+	dev = dev_get_by_index(&init_net, skb->iif);
+	if (!dev) {
+		dev_kfree_skb(skb);
+		return true;
+	}
+
+	/* validate info->control.vif against skb->iif */
+	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
+		sdata = container_of(sdata->bss,
+				     struct ieee80211_sub_if_data,
+				     u.ap);
+
+	if (unlikely(info->control.vif && info->control.vif != &sdata->vif)) {
+		dev_kfree_skb(skb);
+		result = true;
+		goto out;
+	}
+
+	if (info->flags & IEEE80211_TX_INTFL_NEED_TXPROCESSING) {
+		ieee80211_tx(dev, skb, true);
+	} else {
+		hdr = (struct ieee80211_hdr *)skb->data;
+		sta = sta_info_get(local, hdr->addr1);
+
+		ret = __ieee80211_tx(local, &skb, sta);
+		if (ret != IEEE80211_TX_OK)
+			result = false;
+	}
+
+ out:
+	dev_put(dev);
+
+	return result;
+}
+
 /*
  * Transmit all pending packets. Called from tasklet, locks master device
  * TX lock so that no new packets can come in.
@@ -1835,9 +1931,8 @@
 {
 	struct ieee80211_local *local = (struct ieee80211_local *)data;
 	struct net_device *dev = local->mdev;
-	struct ieee80211_hdr *hdr;
 	unsigned long flags;
-	int i, ret;
+	int i;
 	bool next;
 
 	rcu_read_lock();
@@ -1868,13 +1963,8 @@
 
 		while (!skb_queue_empty(&local->pending[i])) {
 			struct sk_buff *skb = skb_dequeue(&local->pending[i]);
-			struct sta_info *sta;
 
-			hdr = (struct ieee80211_hdr *)skb->data;
-			sta = sta_info_get(local, hdr->addr1);
-
-			ret = __ieee80211_tx(local, &skb, sta);
-			if (ret != IEEE80211_TX_OK) {
+			if (!ieee80211_tx_pending_skb(local, skb)) {
 				skb_queue_head(&local->pending[i], skb);
 				break;
 			}